reply to post by pianopraze
What it actually says about pre-1850 measurements itself - rather than taking paraphrasing from critics:
Measurements suitable for showing how surface temperature has changed with time
across the world became available around 1850.
So apparently there was a technological advance about then that made this aspect useable.
Measurements show that averaged over the globe, the surface has warmed by about
0.8oC (with an uncertainty of about ±0.2oC) since 1850.
- not particularly relevant to the dismissal croticism, but included for completeness (it's jsut 1 para below the one above)
and
Observations are not yet good enough to quantify, with confidence, some aspects of
the evolution of either climate forcing or climate change, or for helping to place tight
bounds on the climate sensitivity. Observations of surface temperature change before
1850 are also scarce.
So they are "scarce" - not dismissed at all!!
And that is it - there are no other references to pre-1850 data.
So they say they have little useable data prior to 1850.
To me it looks like something happened in 850 such as a technology change or perhaps an organisational change (eg a national weather monitoring system
was introduced somewhere or something like that).
Presumably you think there is plenty of data prior to 1850 that they could use?
You have mentioned a number of warm spells - but are they sufficiently detailed to be used in a comparison of surface temperatures, which is what htey
are actualy measuring?
We have information from things like growth rings on trees and ice cores that tell us times were warmer or colder, and AFAIK we make "guestimates"
about the temperatures at those times in a general sense - but the modern measurement is a lot more specific than that - it looks at repeated accurate
measurements at set locations over teh last 160 years (more or less) - that is something quite different from the sorts of things I thnk you are
saying they are "ignoring".